1. Field of the Invention
The present invention relates to a display device comprising a plastic sheet of material stretched taut across an annular frame.
2. Prior Developments
U.S. Pat. No. 4,709,928 to Willingham discloses a circular game board formed by an annular circular frame and a sheet of flexible material, said flexible sheet having edge areas thereof secured to the frame by means of an annular sleeve. The frame is formed of a material having a spring characteristic whereby the frame tends to assume a circular hoop-like configuration. The sheet of flexible material can be leather or plastic.
U.S. Pat. No. 4,832,652 to Matsuyama shows and describes a circular foldable toy comprising an annular hoop-like frame, and a sheet of material stretched across the frame. The frame is described as a continuous metal or plastic leaf spring having elasticity and some rigidity. The sheet of material is described as a film made of vinyl chloride or nylon. The patentee indicates that the flexible sheet may have printed indicia thereon, e.g., a picture or lettering.
The present invention relates to a poster which, in a preferred form, comprises an annular circular frame, and a thin plastic sheet stretched taut across the frame. One or both surfaces of the sheet may have indicia thereon, whereby the poster can be used as a sign or a placard. The poster has a variety of uses. It may be used in political campaigns or in political conventions to promote a political candidate or a political cause. A poster having a relatively large diameter, e.g., twenty inches, may be hung from an overhead support or held in a person's hand for waving or movement above the person's head. A poster having a smaller diameter, e.g., seven inches or less, may be attached to a person's coat or shirt to be visible to other persons.
Devices according to the present invention are adapted for other uses. The plastic sheet surface can be used as a writing surface in the nature of a portable blackboard. Various types of pens and "magic" markers have been developed for writing on plastic surfaces.
Plastic sheet materials are well suited for use in signs or posters because of their smooth lustrous surfaces that accept printing inks without running or spreading, and the indicia applied are sharp and distinct. However, plastic sheet materials must be constrained against flexing and wrinkling in order to prevent distortion and design tenuity of printed indicia. The present invention maintains the plastic sheet in a flat, taut condition by maintaining the sheet stretched across a frame.
It has been found in practice that temperature changes and humidity changes can adversely affect the tautness of the sheet on the mounting frame, especially when the sheet-frame assembly is folded during storage, as in the general manner described in the above-mentioned patents, Nos. 4,709,928 and 4,832,652. The adverse effect is a wrinkling or waviness in the plastic sheet, such that the printed indicia becomes distorted and/or discontinuous as viewed.